Oxidative stress is present in Alzheimer's disease (AD) brain, and we recently provided evidence that protein oxidation and lipid peroxidation are also present in brains of persons with mild cognitive impairment (MCI). Our lab first used redox proteomics to identify oxidatively modified proteins in AD and MCI brain. One protein that is oxidatively modified and dysfunctional in both AD and MCI is Pin1, a regulatory protein of many functions relevant to neurodegeneration. One source of oxidative stress in AD is amyloid beta-peptide (AP). The single methionine (Met) of Ap appears to be critical to the oxidative stress induced by Ap. Our overall hypothesis is A(3-mediated oxidative modification of brain Pin1 is fundamental to the progression of AD and occurs via mechanisms involving the single Met of AfJ. To test this overall hypothesis, a series of Specific Aims are proposed. In Specific Aim 1, oxidative stress indices and redox proteomics of preclinical AD (PCAD) brain will be undertaken to test the hypothesis that Pin 1 is oxidatively modified and must be important in the progression of AD. In Specific Aim 2, to determine the temporal role of toxic aggregated AP in the in vivo oxidative modification of Pin 1, we will use redox proteomics to test the hypothesis that in human mutant APP/PS-1 knock in mice oxidative modification and dysfunction of Pin1 will occur. In Specific Aim 3, we will test the hypothesis that Pin 1 in neuronal cultures will be oxidatively dysfunctional by aggregated toxic forms of Ap. In Specific Aim 4, we will test the hypothesis that in vivo elevation of Pin 1 will result in decreased levels of phospho-tau and Ap in brain of APP/PS-1 mice. In Specific Aim 5, we will test the hypothesis that mechanisms involving the single Met residue of Ap are paramount in the in vivo toxic properties of Ap, including the oxidative modification of Pin1. In each Aim, correlation of the status of Ap (type, solubility, oligomerization, etc. determined by Core B) will be made. This proposal reflects a set of comprehensive and integrated studies that utilizes a variety of novel methodologies and that takes advantage of our expertise in oxidative stress, Ap, and redox proteomics applied to AD. Dr. K.P. Lu (Harvard), an acknowledged leader in Pin 1 research, will serve as a Senior Investigator and provide additional expertise. New insights into the oxidative stress, neurodegeneration and progression of AD are envisaged, as are insights into a potential treatment to slow or disrupt progression of MCI to AD.